Axial chiral organic material and circularly polarized electroluminescent application thereof

Abstract

The invention discloses an axially chiral organic material and circularly polarized electroluminescent application thereof, and relates to the technical field of organic electroluminescent materials. The material has a stable molecular structure, rotation limitation between octahydrobinaphthalene rings endows the material with axial chiral characteristics, and by connecting one side of a chiral axis with an s-triazine structure with a classical electron transfer property, stable chiral optical properties can be obtained while the rigidity of the molecular structure is ensured; meanwhile, the thermal stability and the transmission characteristic of the material are also remarkably improved. When the material is applied to a hole blocking layer of an organic light-emitting diode (OLED), due to the advantages of rigidity, structural stability and good chiral characteristic, the spin direction in the electron transmission process can be effectively regulated and controlled, and a remarkable chiral induced spin selective effect is generated. Due to the characteristic, an OLED (Organic Light Emitting Diode) prepared on the basis of the material can generate circular polarization electroluminescence, and compatibility of high electroluminescence external quantum efficiency and high circular polarization electroluminescence asymmetric factors is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electroluminescent materials, and specifically, to an axially chiral organic material and its application in circularly polarized electroluminescence. Background Art

[0002] Circularly polarized light (CPL) is an electromagnetic wave with a constant amplitude, and its electric vector rotates in a spiral manner in the propagation direction. This unique optical property makes it show significant advantages in many cutting-edge technical fields, including optical spintronics, optical quantum information processing, high-density optical data storage, and naked-eye three-dimensional display, etc. Organic light-emitting diodes (OLEDs), as the core devices of electroluminescence (EL), have wide applications in the fields of display and lighting. An OLED is composed of a conductive anode, a hole transport layer (HTL), a light-emitting layer (EML), an electron transport layer (ETL), and a conductive cathode stacked in sequence. Under the drive of an external electric field, electrons and holes are respectively injected from the cathode and the anode, migrate through the transport layer to the light-emitting layer, and finally recombine to form excitons and emit light.

[0003] In the actual use process of an OLED, at least 50% of the energy loss will occur when the unpolarized light emitted by it passes through an antireflection coating. When the electroluminescent material of the OLED is a chiral light-emitting molecule, circularly polarized electroluminescence (CPEL) can be directly and effectively realized, and this type of device is called a circularly polarized organic light-emitting diode (CP-OLED). Because it can theoretically achieve zero energy loss when passing through the coating material, CP-OLED has good application prospects in display screens. In addition, if a chiral functional material is introduced into the transport layer, the spin state of carriers can be regulated through the chiral-induced spin selectivity (CISS) effect, thereby directly generating CPEL, providing a key technical path for the next-generation spintronic devices.

[0004] As can be seen from the above, it is of great significance to develop high-performance circularly polarized organic electroluminescent materials and corresponding CP-OLEDs. However, so far, most of the research has applied chiral materials to the light-emitting layer and it is difficult to simultaneously achieve a high maximum external quantum efficiency (EQE max ) and electroluminescence asymmetry factor (g EL ). Summary of the Invention

[0005] Aiming at the deficiencies of the above-mentioned prior art, the present invention provides an axially chiral organic material and its application in circularly polarized electroluminescence.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] An axially chiral organic material is an organic material based on an axially chiral octahydrobinaphthalene skeleton, and its structural general formula is shown as Formula 1 and Formula 2 below:

[0008]

[0009] In the above general formula, R is selected from hydrogen, alkenyl, alkynyl, amino, nitro, carbonyl, sulfonyl, halogen, cyano, alkoxy, substituted C6-C60 aromatic ring groups, unsubstituted C7-C60 aromatic ring groups, substituted or unsubstituted C3-C60 heteroaromatic ring groups.

[0010] Specifically, the chiral organic material is any one of the following structural formulas:

[0011]

[0012] Of course, the compounds P1-P12 shown in the above structures may correspondingly include isomers with S-type and R-type chiral absolute configurations.

[0013] Another object of the present invention is to provide the application of the chiral organic material as a circularly polarized organic electroluminescent material in electronic devices.

[0014] Specifically, the electronic device is an organic electroluminescent device, an organic solar cell, an organic field effect transistor, an organic light-emitting field effect transistor, an organic laser, an organic sensor or an organic spintronic device.

[0015] Further, the electronic device is an organic electroluminescent device, the organic electroluminescent device includes a functional layer, and the functional layer is composed of 0.1-100% by mass of the chiral organic light-emitting material and 0-99.9% by mass of an organic functional material.

[0016] Further, the organic functional material is selected from one of a hole injection material, a hole transport material, a hole blocking material, an electron injection material, an electron transport material, an electron blocking material, an exciton blocking material, a fluorescent material, a phosphorescent material, a host material and an organic dye.

[0017] Further, the electronic device is an organic electroluminescent device, and the organic electroluminescent device includes an electron transport layer, and the electron transport layer includes the chiral organic material.

[0018] Further, the organic electroluminescent device may be an inverted structure or a normal structure; of course, according to needs, a hole injection layer and / or an electron transport layer, etc. may also be provided between the anode and the light-emitting layer. When both a hole injection layer and an electron transport layer are provided, the hole injection layer is disposed closer to the anode side, and the electron transport layer is disposed closer to the light-emitting layer side; an electron injection layer and / or an electron transport layer, etc. may also be provided between the cathode and the light-emitting layer. When both an electron injection layer and an electron transport layer are provided, the electron injection layer is disposed closer to the cathode side, and the electron transport layer is disposed closer to the light-emitting layer side. The materials and thicknesses of the anode, cathode, hole injection layer, electron transport layer, electron injection layer, electron transport layer of the organic electroluminescent device, as well as the thickness of the light-emitting layer, can all be set according to existing organic electroluminescent devices.

[0019] The above-mentioned electronic device can be applied to an electronic device. For example, a display panel, and the display panel includes: a substrate and several electronic devices as described above arbitrarily provided on the substrate, and the electronic device is an organic electroluminescent device.

[0020] Specifically, the substrate can be rigid or flexible.

[0021] Advantages of the present invention:

[0022] The material of the present invention has a rigid and stable axial chiral structure, and the chirality is due to the restricted rotation between two octahydrobinaphthalene rings; by selecting different functionalized substituents, the skeleton structure of the binaphthalene unit can be further modified to provide a good chiral induction effect; on the other hand, the stable axial chirality in chiral octahydrobinaphthylamine can make the organic material have obvious circular dichroism. When it is applied to the OLED electron transport layer, based on the chiral-induced spin selectivity effect, the corresponding circularly polarized electroluminescent OLED achieves a high EQE max and g EL . BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] Figure 1 Schematic diagram of the synthesis route of the axial chiral organic material P1 (R configuration) in Example 1;

[0025] Figure 2 Schematic diagram of the synthesis route of the axial chiral organic material P1 (S configuration) in Example 2;

[0026] Figure 3 Structural diagram of the OLED device based on compound P1 in Example 3;

[0027] Figure 4The OLED electroluminescence spectrum based on compound P1 in Example 3;

[0028] Figure 5 The circularly polarized electroluminescence spectrum of the OLED based on compound P1 in Example 3;

[0029] Figure 6 The circularly polarized electroluminescence asymmetry factor of the OLED based on compound P1 in Example 3;

[0030] Figure 7 The maximum external quantum efficiency of the OLED based on compound P1 in Example 3. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Example 1: Synthesis of R-configuration P1 (as Figure 1 shown)

[0033] P1 can be synthesized from (R)-5,5',6,6',7,7',8,8'-octahydro-[1,1'-binaphthalene]-2,2'-diiodide and 1,3,5-triphenylboronic acid pinacol ester-triazine, and P1 can be generated through Suzuki-Miyaura coupling.

[0034] Among them, 1,3,5-triphenylboronic acid pinacol ester-triazine can be obtained in one step by Suzuki-Miyaura coupling reaction of 2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine and bis(pinacolato)diboron. According to Figure 2 , under argon protection, 2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine (777 mg, 2 mmol), bis(pinacolato)diboron ((Bpin)2, 508 mg, 2 mmol), [1,1']-bis(diphenylphosphino)ferrocene] dichloropalladium (Pd(dppf)Cl2, 14.6 mg, 0.2 mmol), potassium acetate (KOAc, 196 mg, 2 mmol) and 10 ml of dry 1,4-dioxane were added to a 25 ml round-bottom flask. The mixture was heated and stirred for 24 h, cooled to room temperature, extracted with dichloromethane (3 × 100 mL) and water (100 mL), and then dried by rotary evaporation. Column chromatography was carried out with a volume ratio of petroleum ether:dichloromethane of 5:1 to obtain 0.566 g of white solid with a yield of 65%. HRMS (ESI): m / z [M+H] +: 436.2199.

[0035] According to Figure 1 , under the protection of argon gas (Ar), (R)-5,5',6,6',7,7',8,8'-octahydro-[1,1'-binaphthalene]-2,2'-diiodide (Compound 1, 514 mg, 1 mmol), 1,3,5-triphenylboronic acid pinacol ester-triazine (1.31 g, 3 mol), tetrakis(triphenylphosphine)palladium (Pd(PPh3)4, 116 mg, 0.1 mmol), potassium carbonate (K2CO3, 414 mg, 3 mmol) and 15 ml of dry toluene / ethanol / water were added to a 50 ml round-bottom flask. The mixture was heated and stirred for 24 h and then cooled to room temperature. It was extracted with dichloromethane (3 × 200 mL) and water (200 mL) and then concentrated by rotary evaporation. Column chromatography was carried out with a volume ratio of petroleum ether:ethyl acetate of 10:1, and then recrystallized with a cyclohexane / petroleum ether solvent system to obtain 0.415 g of a white solid with a yield of 46%. HRMS(ESI): m / z [M + H] + : 909.4640.

[0036] Example 2: Synthesis of S-configuration P1 (as Figure 2 shown)

[0037] P1 can be synthesized from (S)-5,5',6,6',7,7',8,8'-octahydro-[1,1'-binaphthalene]-2,2'-diiodide and 1,3,5-triphenylboronic acid pinacol ester-triazine, and P1 can be generated through Suzuki-Miyaura coupling.

[0038] According to Figure 2 , under the protection of argon gas, (S)-5,5',6,6',7,7',8,8'-octahydro-[1,1'-binaphthalene]-2,2'-diiodide (Compound 1, 514 mg, 1 mmol), 1,3,5-triphenylboronic acid pinacol ester-triazine (1.31 g, 3 mol), tetrakis(triphenylphosphine)palladium (Pd(PPh3)4, 116 mg, 0.1 mmol), potassium carbonate (K2CO3, 414 mg, 3 mmol) and 15 ml of dry toluene / ethanol / water were added to a 50 ml round-bottom flask. The mixture was heated and stirred for 24 h and then cooled to room temperature. It was extracted with dichloromethane (3 × 200 mL) and water (200 mL) and then concentrated by rotary evaporation. Column chromatography was carried out with a volume ratio of petroleum ether:ethyl acetate of 10:1, and then recrystallized with a cyclohexane / petroleum ether solvent system to obtain 0.498 g of a white solid with a yield of 54%. HRMS(ESI): m / z [M + Na] + : 931.4468.

[0039] Example 3: OLED Based on Compounds P1 with Different Chiral Configurations and Its Performance Tests Specifically according to the structure of the OLED: Anode / Hole Injection Layer / Hole Transport Layer / Electron Blocking Layer / Light-Emitting Layer / Hole Blocking Layer (doped with the above chiral organic material P1 and a material, and then stacked with another material) / Electron Transport Layer / Electron Injection Layer / Cathode. Prepare OLEDs based on compounds P1 with different chiral configurations and test their performances respectively.

[0040] Device 1: ITO (Anode) / HATCN (5 nm) (Hole Injection Layer) / TAPC (30 nm) (Hole Transport Layer) / TCTA (15 nm) (Hole Transport Layer) / mCBP (10 nm) (Electron Blocking Layer) / DMIC-TRZ:Ir(ppy)3:BN2 (40 nm) (Light-Emitting Layer) / POT2T:15 wt% (R)-P1 (20 nm) (Hole Blocking Layer) / ANT-BIZ (30 nm) (Electron Transport Layer) / Liq (2 nm) (Electron Injection Layer) / Al (Cathode).

[0041] Device 2: ITO (Anode) / HATCN (5 nm) (Hole Injection Layer) / TAPC (30 nm) (Hole Transport Layer) / TCTA (15 nm) (Hole Transport Layer) / mCBP (10 nm) (Electron Blocking Layer) / DMIC-TRZ:Ir(ppy)3:BN2 (40 nm) (Light-Emitting Layer) / POT2T:15 wt% (S)-P1 (20 nm) (Hole Blocking Layer) / ANT-BIZ (30 nm) (Electron Transport Layer) / Liq (2 nm) (Electron Injection Layer) / Al (Cathode).

[0042] Among them, the structural formulas of HATCN, TAPC, TCTA, mCBP, DMIC-TRZ, Ir(ppy)3, BN2, POT2T, ANT-BIZ, and Liq are as follows:

[0043]

[0044] Indium tin oxide conductive glass (ITO) was successively ultrasonically cleaned with deionized water, acetone, and isopropyl alcohol, and then treated with ultraviolet ozone. Then, each organic layer and the cathode Al layer were successively evaporated under high vacuum conditions, and the OLED was encapsulated in a glove box. The preparation of the device strictly followed the standard procedure. Among them, the substrate was transparent glass, the anode was indium tin oxide conductive glass (ITO), the cathode was metal aluminum, and each functional layer was evaporated layer by layer between the anode and the cathode. The pretreatment of the ITO glass strictly followed the standard procedure. First, the surface of the ITO glass was wiped with cotton soaked in acetone or ethanol, then the cotton fluffs on the surface were washed away with deionized water, and then it was ultrasonically cleaned with acetone and ethanol for 10 min in turn; dried with nitrogen, and the surface of the ITO glass was irradiated with a ultraviolet-ozone surface treatment instrument (PL16) for 20 min. All evaporation processes were carried out in a cavity with a vacuum degree lower than 10 -4 Pa; during the evaporation process, the deposition rate of the organic layer was controlled at 0.1 - 0.2 nm s -1 . The light-emitting layer and the electron transport layer were co-evaporated from different organic sources, and the doping ratio was controlled by controlling the relative evaporation rate of the organic sources.

[0045] The effective light-emitting area of the OLED was determined to be 1×1 mm 2 , the electroluminescence signal was collected by an integrating sphere, and after correction by the Lambertian distribution of the spectrum, the external quantum efficiency of the OLED was obtained; the circularly polarized spectrum of the OLED was tested using a circularly polarized fluorescence spectrometer CPL-300. The measured results of the performance of the OLED based on compounds P1 with different chiral configurations are shown in Table 1, and the characterization spectra of each performance are as Figures 3 - 7 . It can be seen that the above chiral organic materials can be introduced into the electron transport layer of the OLED to prepare highly efficient CP-OLEDs.

[0046] Table 1 Performance test results of OLEDs based on different chiral configurations of P1

[0047]

[0048] In summary, the present invention provides chiral organic materials and their applications. The chiral organic materials based on the octahydrobinaphthalene skeleton have a rigid and stable axial chiral structure. The chirality is due to the restricted rotation between two octahydrobinaphthalene rings. The skeleton structure of the hydrobinaphthalene unit can be further modified by selecting different functionalized substituents to provide a good chiral induction effect; on the other hand, the stable axial chirality in chiral octahydrobinaphthylamine can endow the organic material with circular dichroism. When it is applied to the hole blocking layer of the OLED, based on the chiral-induced spin selectivity effect, the corresponding circularly polarized electroluminescent OLED achieves a relatively high EQE max and g EL .

[0049] The above specific implementation manners have specifically introduced the analysis method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and idea of the present invention, rather than a limitation on the relevant content. Without departing from the principle of the present invention, those skilled in the art can also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications should also fall within the protection scope of the present invention.

Claims

1. An axially chiral organic material, characterized in that, It is an organic material based on an axially chiral octahydrobinaphthalene skeleton, and the general structural formula is shown as Formula 1 and Formula 2 below: In the above general formula, R is selected from hydrogen, alkenyl, alkynyl, amino group, nitro group, carbonyl group, sulfone group, halogen, cyano group, alkoxy group, substituted C6-C60 aromatic ring group, unsubstituted C7-C60 aromatic ring group, substituted or unsubstituted C3-C60 heteroaromatic ring group.

2. The axially chiral organic material according to claim 1, wherein The chiral organic material is any one of the following structural formulas:

3. Application of the chiral organic material according to claim 1 or 2 as a circularly polarized organic electroluminescent material in an electronic device.

4. The application according to claim 3, characterized in that, The electronic device is an organic electroluminescent device, an organic solar cell, an organic field effect transistor, an organic light-emitting field effect transistor, an organic laser, an organic sensor or an organic spintronic device.

5. The application according to claim 3, characterized in that, The electronic device is an organic electroluminescent device, and the organic electroluminescent device includes a functional layer, and the functional layer is composed of 0.1-100% by mass of the chiral organic light-emitting material and 0-99.9% by mass of an organic functional material.

6. The application according to claim 5, characterized in that, The organic functional material is selected from one of a hole injection material, a hole transport material, a hole blocking material, an electron injection material, an electron transport material, an electron blocking material, an exciton blocking material, a fluorescent material, a phosphorescent material, a host material and an organic dye.

7. The application according to claim 3, characterized in that, The electronic device is an organic electroluminescent device, and the organic electroluminescent device includes an electron transport layer, and the electron transport layer includes the chiral organic material.

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